Finding count of records in given interval - sql-server

Question

I have a table with user logins, and I want to find the user who logged in to the site more than 3 times in a 5 day period.
For example my table is:
id | user_id | login_date
---+---------+--------------
1 | 10 | 10.1.2014 00:00
2 | 10 | 11.1.2014 10:10
3 | 12 | 11.1.2014 11:00
4 | 10 | 11.1.2014 12:00
5 | 12 | 12.1.2014 00:00
6 | 10 | 13.1.2014 10:00
7 | 12 | 18.1.2014 00:00
8 | 12 | 22.1.2014 09:00
For this example table, I want to choose user_id 10 because he/she logged in more than 3 times in a 5 day period.
Could you please help me for that?
edit: i forgot to mention that database is sql server 2008

Answer 1

You could do it by self joining the table on user_id where the JOIN takes records that are within 5 days of the record it is joining to like so:
CREATE TABLE #login
(
id INT ,
user_id INT ,
login_date DATETIME
)
INSERT INTO #login
( id, user_id, login_date )
VALUES ( 1, 10, '2014-01-10 00:00' ),
( 2, 10, '2014-01-11 10:10' ),
( 3, 12, '2014-01-11 11:00' ),
( 4, 10, '2014-01-11 12:00' ),
( 5, 12, '2014-01-12 00:00' ),
( 6, 10, '2014-01-13 10:00' ),
( 7, 12, '2014-01-18 00:00' ),
( 8, 12, '2014-01-22 09:00' )
SELECT t1.user_id ,
t1.login_date AS FirstDateInLoginPeriod ,
COUNT(t2.user_id) AS LoginCount
FROM #login t1
INNER JOIN #login t2 ON t2.user_id = t1.user_id
AND t2.login_date
BETWEEN t1.login_date AND DATEADD(DAY, 5, t1.login_date)
GROUP BY t1.user_id ,
t1.login_date
HAVING COUNT(t2.user_id) > 3
DROP TABLE #login
Produces:
user_id FirstDateInLoginPeriod LoginCount
----------------------------------------------
10 2014-01-10 00:00:00.000 4

Answer 2

If you are using SQL Server 2012+ then you can use LEAD window function to calculate difference in days between any 3 consecutive records:
select distinct USER_ID
from (
select USER_ID,
datediff(d, login_date,
LEAD(login_date, 2) OVER (PARTITION BY user_id
ORDER BY login_date)) as diffDates
from users ) t
where t.diffDates <= 5
Then simply select those USER_IDs for which the difference in days is equal to or less than 5.
SQL Fiddle Demo
If you are using SQL Server 2008 or 2005, then you can use ROW_NUMBER in conjuction with a self join in order to simulate LEAD function:
;WITH CTE AS (
SELECT id, user_id, login_date,
ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY login_date) AS rn
FROM users
)
SELECT DISTINCT user_id
FROM (
SELECT c1.user_id,
DATEDIFF(d, c1.login_date, c2.login_date) AS diffInDays
FROM CTE AS c1
INNER JOIN CTE AS c2 ON c1.user_id = c2.user_id AND c1.rn = c2.rn - 2
) t
WHERE t.diffInDays <= 5
diffInDays in the above query is essentially the rolling difference in days between any 3 consecutive user logins.
SQL Fiddle Demo

Answer 3

You can use following query to get your result.
As you can see you can use DATEADD function for calculating reference date and use having to filter logins count to be more or equal 3
Select count(*),user_id
from table_name
where login_date>=DATEADD (day,-5,GETDATE())
group by user_id
having COUNT(*) >=3